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6CCVD Research

Magnetic Steganography Based on Wide‐Field Diamond Quantum Microscopy

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-05-12
JournalAdvanced Optical Materials
AuthorsJungbae Yoon, Jugyeong Chung, Hyunjun Jang, Ji Eun Jung, Yuhan Lee
InstitutionsKorea University, Chosun University
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research demonstrates a novel magnetic steganography technique utilizing wide-field diamond Nitrogen-Vacancy (NV) quantum microscopy, offering enhanced security and imaging speed compared to conventional methods.

  • Concealed Information Retrieval: Successfully revealed hidden magnetic patterns (pixel art, barcodes, QR codes) fabricated using Nickel (Ni, magnetic) and Gold (Au, non-magnetic) mixtures, which are optically indistinguishable.
  • Wide-Field Capability: Achieved magnetic imaging over millimeter-sized areas with a spatial resolution of less than 1 µm, suitable for large-scale security applications.
  • Expedited Imaging: Implemented a Continuous Wave (CW) dual driving scheme, simultaneously manipulating the NV qutrit states (ms = 0 ↔ ms = ±1).
  • Performance Gain: The dual driving method reduced the required imaging time by a factor of three and provided a 1.5-2.0 times enhancement in DC magnetic sensitivity.
  • Optimal Imaging Mode: ODMR contrast mapping was identified as the superior mode for reconstructing hidden magnetic structures, offering better image quality than frequency shift (B field) or linewidth mapping.
  • Digital Encoding: Demonstrated encoding of digital data, including website links and text messages, into the magnetic patterns, validating the approach for digital security applications.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
NV Center Depth15 ± 5nmDepth from the diamond surface.
NV Center Density~10ppmConcentration of NV ensemble.
Diamond GradeElectronic Grade [100]N/ASubstrate material (2 x 2 x 0.1 mm3).
NV Creation Method15N+ ImplantationN/APerformed at 10 keV, followed by 1200 °C annealing.
Green Laser Wavelength532nmExcitation source for NV fluorescence.
Green Laser Power700mWUsed in Total Internal Reflection Fluorescence (TIRF) setup.
Microwave Frequency~2.9GHzUsed to drive NV spin transitions (ODMR).
External Magnetic Field (Bext)~400GApplied to separate Zeeman-split resonance pairs.
Spatial Resolution<1µmLimited by the optical diffraction limit.
Magnetic Feature Size1 x 1 to 2 x 2µm2Dimensions of Ni/Au dots/bars in steganography samples.
Imaging Time ReductionFactor of 3N/AAchieved using the CW dual driving scheme.
Sensitivity Enhancement1.5 - 2.0N/AImprovement factor of DC magnetic sensitivity with dual driving.

Key Methodologies

Section titled “Key Methodologies”

The experiment combined advanced nanofabrication with wide-field quantum microscopy techniques.

  1. Diamond Sensor Fabrication:
    • A 100 µm thick diamond plate was implanted with 15N+ ions (10 keV) to create an ensemble of NV centers (~15 nm deep).
    • The diamond was annealed at 1200 °C and subsequently treated with oxygen termination (465 °C) to stabilize the NV charge state.
  2. Magnetic Pattern Lithography:
    • Magnetic (Ni) and non-magnetic (Au) patterns were fabricated on a cover glass using Electron Beam Lithography (EBL) and lift-off processes.
    • Patterns included a 10 nm Titanium adhesion layer followed by 50 nm of the functional metal (Au or Ni).
    • Precise alignment during sequential EBL steps ensured the creation of mixed-material structures (e.g., 2 µm Ni dots interspersed with 2 µm Au dots).
  3. Wide-Field ODMR Measurement Setup:
    • The diamond was placed over an Omega-shaped gold microwave waveguide.
    • NV centers were excited using a 532 nm green laser focused through a TIRF objective (N.A. = 1.49).
    • Fluorescence was collected and imaged by a scientific Complementary Metal-Oxide-Semiconductor (SCMOS) camera.
  4. Magnetic Image Acquisition:
    • ODMR spectra were measured pixel-by-pixel across the field of view.
    • Magnetic images were generated by mapping three parameters derived from the ESR dips: frequency shift (B field), linewidth, and contrast.
  5. Dual Driving Implementation:
    • To expedite imaging, two independent microwave fields were applied simultaneously to drive both the ms = 0 ↔ ms = -1 and ms = 0 ↔ ms = +1 transitions (qutrit states).
    • This dual driving method increased the overall ODMR contrast by reducing the population of the ms = 0 state, thereby improving sensitivity and reducing measurement time.

Commercial Applications

Section titled “Commercial Applications”

This technology has significant potential in security, sensing, and advanced manufacturing sectors, leveraging the unique capabilities of NV quantum microscopy.

  • High-Security Anti-Counterfeiting:
    • Manufacturing secure documents, currency, and high-value product tags with embedded magnetic barcodes or QR codes that are impossible to replicate or detect using standard optical scanners.
    • The hidden information (e.g., serial numbers, authentication keys) requires a specialized quantum magnetometer for retrieval.
  • Forensic Science and Digital Security:
    • Creating covert communication channels or physical storage media where data is encoded magnetically at the micrometer scale, offering a high degree of confidentiality.
  • Advanced Magnetic Sensing and Metrology:
    • Developing high-speed, wide-field magnetometers for industrial inspection and quality control of magnetic components and films.
    • Characterization of stray magnetic fields from microelectronic devices and current transport systems.
  • Quantum Imaging Platforms:
    • Commercialization of wide-field NV quantum microscopes optimized for rapid, large-area imaging, utilizing the demonstrated dual driving scheme for enhanced throughput.
  • Manufacturing Integration:
    • Future integration with high-throughput printing technologies (e.g., piezo inkjet printing) to enable cost-effective, large-scale production of magnetic steganography features.
View Original Abstract

Abstract Magnetic steganography using wide‐field quantum microscopy based on diamond nitrogen‐vacancy (NV) centers is experimentally demonstrated. The method offers magnetic imaging capable of revealing concealed information otherwise invisible with conventional optical measurements. For a proof‐of‐principle demonstration of magnetic steganography, micrometer structures designed as pixel arts, barcodes, and QR codes are fabricated using mixtures of magnetic and non‐magnetic materials: Ni and Au. Three different imaging modes based on the changes in frequency, linewidth, and contrast of the NV’s electron spin resonance are compared and find that the last mode offers the best quality for reconstructing hidden magnetic images. By simultaneous driving of the NV’s qutrit states with two independent microwave fields, the imaging time is expedited by a factor of three. This work shows potential applications of quantum magnetic imaging in the field of image steganography.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2005 - Information Hiding: First International Workshop
  2. 2002 - in Optical Security and Counterfeit Deterrence Techniques IV

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